Fossil fuel, such as coal, crude oil and natural gas, are produced by the decomposition of ancient (fossilized) plants and animals. Fossil fuels are fuels formed by natural resources such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years.These fuels contain a high percentage of carbon and hydrocarbons.
Fossil fuels are hydrocarbons such as coal, oil and natural gas, sourced from the organic remains of prehistoric organisms. When these fuels are burnt, the energy released can be harnessed to produce electricity, power vehicles, heat homes, cook food and much more. They are also used in the production of important materials such as plastic.
Fossil fuels, coal, oil and natural gas, are a non-renewable source of energy. Formed from plants and animals that lived up to 300 million years ago, fossil fuels are found in deposits beneath the earth. The fuels are burned to release the chemical energy that is stored within this resource. Energy is essential to moden society as we know it. Over 85% of our energy demands are met by the combustion of fossil fuels. These two pie charts show exactly how vital fossil fuels are to our society by showing how much of each energy resource is consumed.
Oil and gas are formed from the organic remains of marine organisms which become entrained within sea-floor sediments. Coal, by contrast, is typically formed in non-marine settings from the remains of land vegetation.
Oil and gas formation begins with the accumulation of organics on the sea-floor; these are the dead remains of organisms living in the water column, such as microscopic plankton, which rain down on the sea floor below. This will only occur in rather unusual settings, where the sea floor is stagnant such that there is no oxygen present to break the organic remains down and no sea-floor dwelling organisms present that might feed on the organics. A high sediment accumulation rate of may also help to bury the organics before the action of decay can break them down. As the sediment pile becomes deeper the organics within it are subjected to heat and pressure which leads to formation of oil and then gas. For oil and gas extraction, it is important that the source rock is not 'over-cooked' or the hydrocarbons will be destroyed. There must be suitable reservoir-rock, such as a porous sandstone, into which the hydrocarbons can migrate and accumulate. This must be overlain by an impervious cap-rock, such as a clay, which prevents the hydrocarbons from escaping to the surface. Finally, the geometry of the reservoir and cap-rock bodies must be such that the hydrocarbons become trapped; usually folding will suffice.
Coal typically forms on land from vegetation in lowland, swampy, mire environments. Stagnant waterlogged soil prevents the accumulated plant debris from breaking down. The recognisable remains of plants are often visible within coals and associated shales, confirming their plant-origin. The picture above shows a piece of Coal containing a network of fossilised fern leaves - clear evidence that it was formed from vegetable remains.
The accumulated plant debris initially forms a material known as peat. The geological processes of burial beneath later sediment and alteration by heat and pressure convert the peat to coal; a process known as coalification.
For the peat to become coal, it must be buried by sediment. Burial compacts the peat and, consequently, much water is squeezed out during the first stages of burial. Continued burial and the addition of heat and time cause the complex hydrocarbon compounds in the peat to break down and alter in a variety of ways. The gaseous alteration products (methane is one) are typically expelled from the deposit, and the deposit becomes more and more carbon-rich as the other elements disperse. The stages of this trend proceed from plant debris through peat, lignite, sub-bituminous coal, bituminous coal, anthracite coal to graphite (a pure carbon mineral).
 Combustion, drilling, and refining
Combustion is the process of breaking atomic bonds to release energy in the form of light and heat. Fossil fuels have many hydrocarbons, each with numerous bonds. When they undergo combustion, they release a great deal of heat. This is the main reason why natural gas and heating oils are used extensively in the world today. However, energy in the form of heat is by nature very chaotic and disorganized. Simply burning fossil fuels is wonderful for keeping the winter chill at bay, but setting oil on fire in your washing machine won't get your clothes clean. Likewise, we can't put petroleum directly out of the ground into our cars and expect them to operate. To make use of the resource of fossil fuels, humans have developed drilling, refining, and methods to harness fossil fuel energy.
Early oil explorers relied heavily on intuition and guesswork to find the precious 'black gold.' These daring entrepreneurs were known as 'wildcatters.' A fabled technique used by the wildcatters is the 'old hat.' They would basically toss their hat up in the air and wherever it landed, they drilled. When the wildcatters got lucky, and struck oil, it would typically gush up the drill pipe, hence, a gusher. Because gushers are a safety hazard and environmental concern, oil companies today contain them. After discovering an oil field, it is the task of the oil company's engineers and technicians to get it out. Not all oil fields turn out to be gushers and even the ones that are eventually loose pressure, leaving a lot of untapped fossil fuel resource in the reservoir. Even with modern extraction techniques, 100% of the oil in any given field is still not yet recoverable.
One thing an oil company does to facilitate the extraction process is setting up what is known as a 'Christmas tree,' a system of valves and pipes that regulate oil flow and pressure. Another system used in much smaller reservoirs not worth the expense of manning with technicians is the setup of a beam pump These are also known as 'nodding donkeys;' they extract oil from small oil pools that do not contain much resource. In large oil fields, techniques such as water and gas injection are employed to maximize return of the investment. By pumping water and gas into the wells, the pressure increases allowing oil to flow upwards once more Large oil fields can be found under the sea floor as well. To exploit these fields, vast oil drilling stations, which are marvels of modern engineering, tap into these underwater deposits and bring them to the surface.
Although fossil fuels have been around long before humans even discovered fire, our prehistoric ancestors had no use for them. In the late 1800's, coal and gas were used as heat and light sources, steam locomotives as well. There were early automobiles too, but these vehicles were more of a novelty than a way of life. It wasn't until the 1940's did things change. Why the 1940's? The answer is that engineers and inventors had government support and extra incentive to develop fossil fuel technologies, war. World War II was the catalyst and not World War I because 'The War to End All Wars' was fought by men in trenches and mechanized warfare had only been developed late in the conflict. World War II had the German Blitzkrieg, or 'Lightning War.' This tactic utilized Shtuka dive bombers and Panzer tanks; German engineers enabled this, and was eventually countered by Allied technological advancements. From then on, usage and development of fossil fuels steadily rose.
The primary refining technique used to separate hydrocarbons and provide the ingredients for modern fuels is called fractional distillation. Hydrocarbons of different size and configuration usually have differences in boiling points that are large enough to use as a method of separation. By vaporizing them, they tend to float upwards until the hydrocarbons condense, which is where they are collected. Hydrocarbons as simple as butane and alcohols with few carbons are sorted along with more complex ones such as aromatics with 9 carbons. The fuels we commonly use today are a mixture of these hydrocarbons distilled from the petroleum extracted from the earth.
 Fuel types and engines
Gasoline is a highly specialized fuel that contains hydrocarbons ranging from butane to C10. It is designed for the Otto-cycle engine, also known as spark ignition or 4-stroke engine. This engine as well as others will be described in more detail later on. Some characteristics of gasoline enable the following:
- Quick start at low temperatures
- Fast acceleration
- Low occurrence of stalling
- Relatively quiet and low tendency to knock
- Good combustion efficiency
The next classification of fuels is the distillate fuels. They are kerosene, turbo-jet fuel, diesel, and heating oil. Kerosene was the first petroleum fuel oil to be widely used; this was before electric lights and after the days of animal and vegetable oil. Kerosene has become less popular and is no longer produced in the quantities it once was. Countries with limited access to electricity and outdoors enthusiasts still have a use for this fuel.
Turbo-jet fuel was first developed in WWII for use in airplane engines. Because of constraints on petroleum products, namely gasoline for tanks and other ground vehicles, this fuel was designed to make use of compounds not vital to gasoline production whenever possible. The result was a highly volatile fuel that led to many accidents in handling. Modern aviation fuel is still more volatile than gasoline, though it has become much safer than it previously was.
Diesel fuel and domestic heating oil are similar in composition. Domestic heating oils are not widely used in the US, though they still have limited application in underdeveloped countries. Diesel fuels are used frequently in the world today; transport vehicles such as trains, boats, trucks, and buses use diesel fuel.
Fuel oils are mainly residuals from the fractional distillation process. They are more or less the leftovers from production of other fuels. They have been and are still used in power generation plants. Because of the low quality and high pollution content fuel oils are being used less often.
Of the fuels previously listed, gasoline, turbo-jet fuel, and diesel fuel were designed for usage in engines. A fairly good, simple definition of an engine is a device that converts chemical or heat energy into mechanical energy. Engines convert fossil fuel energy into a form that we can more readily use.
The majority of engines in the world today are internal combustion engines. This type of engine is found in most machines and vehicles that run on fossil fuels. The first internal combustion engine was invented by Nicolaus August Otto. There are 4 general types of internal combustion engines that will be discussed here briefly. The first is the type designed by Mr. Otto himself, the Otto-cycle engine. These are the engines you typically find in cars. These are 4-stroke engines, named thus because it goes through 4 phases during operation: intake, compression, expansion, and exhaust. The parts of the engine directly involved in this cycle are the cylinder, the piston, the valves, and the spark plug.
- Intake- Intake valve opesns allowing fuel/air mixture into the cylinder
- Compression- The piston rises, reducing volume and increasing pressure
- Expansion (power stroke- Spark plug ignites, fuel expands pushing piston
- Exhaust- Exhaust valve opens expelling spent fuel from cylinder
The second type of engine is known as a 2-stroke engine. These are usually placed in lawn mowers, outboard motors, and high performance recreational vehicles. There are two main differences between 4 and 2-stroke engines A 4-stroke engine causes two revolutions in one cycle whereas the 2-stroke only takes one revolution to complete its cycle. The other major difference between them is that 2-strokes require a gasoline/oil mixture as fuel. This is because the cylinder must be kept completely bathed in lubricants to prevent damage. Due to these attributes, these engines are much more compact and can generate higher revolutions per minutes and more acceleration. The problem with this design is that it is not at all fuel efficient and burning motor oil causes a lot of pollution.
Diesel engines, as you might know, require no spark plugs in the combustion process. Otherwise, the design of the diesel engine is not much different than an Otto-cycle engine. Instead of spark plugs, the diesel engine relies on compression and the heating of air in the fuel mixture to cause ignition. To achieve this, diesel fuel has a lower boiling point and does not require much heat. Diesel fuel is cheaper to make than gasoline, though its high level of pollutants require it to undergo further filtration; this drives the fuel price up.
The last type of conventional engine discussed here is the wankel rotary combustion engine, named after its inventor, Felix Wankel. Out of the engines discussed, this one is the most 'revolutionary' (excuse the pun). The wankel engine does not use pistons, instead it uses a rotor. The rotor spins and drives the shaft by expanding fuel in the housing on the sides of the rotor. The results of this engine type are as follows:
- Light weight and compact
- Smooth: no reciprocating motion
- Extended power stroke rotation: 270 degrees vs. 180 degrees of a piston
- Fewer moving parts
- Cooler combustion means fewer oxides of nitrogen
The wankel engine was used in the Mazda motorcars RX series of cars. For all the advantages of this engine, it had one major drawback, it was extremely inefficient in fuel consumption. The oil crisis in 1973 caused this engine to loose support and funding for further development to improve consumption. Currently the RX series of Mazda cars is no longer in production, however Mazda has made a RX-01 concept car. Wankel rotary engines can also be found in porches and other powerful sports cars.
Aviation fuel, the turbo-jet fuel, is used by both jet and propeller aircraft today. Prop engines are designed similar to the 4-stroke engines of cars, though the demands on these two varieties of engines are quite different.To accommodate this, prop engines are much larger and have higher power output. The distillate fuel they use is ideal for this purpose. With the inception of jet propulsion the fuels used did not change all that much. Even though it may seem that the jet engine is very different, it is still considered to be an internal combustion engine. The main components of a jet engine are the compressor, combustion chamber, and the turbine. Air flows into the compressor where it is pressurized and forced into the combustion chamber There, inside the chamber, fuel is constantly flowing in, and ignited causing an expansion of the fuel The turbine's purpose is to provide enough energy from the expelled gasses to the compressor in order to operate at peak performance. Jet engine technology has advanced greatly and there are many different types of them. Just to list a few, there are turbojet, turbofan, turboprop, turboshaft, and ramjet designs. Each have specialized uses, mostly in aviation technology.
 Coal and electricity
Fossil fuels are excellent sources of energy for out transportation needs; however they are also the primary source of electrical energy in the world today. Coal power plants account for at least 60% of our national energy and 52% of the world's demand. We, as a world, burn approximately 1.9 billion tons of coal a year to generate electricity.
How we get electrical energy from coal is by means of coal power plants. These power plants first combust the coal in large furnaces creating tremendous amounts of heat. This heat is used to evaporate water in boilers so they convert to steam. The steam expands, causing pressure to increase in the boiler. A steam turbine is placed at the exit of the boiler where it converts energy from the moving steam into mechanical energy. The rotation of this turbine is used to spin a magnet inside a power generator. This generator is a large electromagnet that encases the spinning magnet. Instead of putting electricity into the electromagnet to cause the coil to magnetize, electrons are captured from the spinning magnet and collected. The electrons are then sent to the national power grid where they are distributed as needed.
 Health impacts
Air particles are deadly. The byproducts that form from the burning of fossil fuels are very dangerous. These small particles can exist in the air for indefinate periods of time, up to several weeks and can travel for miles. The particles, sometimes smaller than 10 microns in diameter, can reach deep within the lungs. Particles that are smaller than this can enter the blood stream, irritating the lungs and carry with them toxic substances such as heavy metals and pollutants. Over a lifetime of continued exposure, a person's ability to transfer oxygen and rid pollutants is impeded. Those affected could become afflicted with fatal asthma attacks and other serious lung conditions. the World Resources Institute reports that between the years of 2000 and 2020, 8 million deaths worldwide could possibly occur without changing present conditions. In 1990 alone, respiratory diseases were a leading cause of disabilities and illnesses worldwide. This is a global problem and requires a global solution. Because the contamination is growing at an exponential rate, minor reductions now will greatly reduce the number of lives lost in the future.
 Additional energy statistics
Natural gas accounts for 24% of the energy in the United States. Domestic production of natural gas peaked in 1973; this is because we do not import due to safety problems. Consumption of natural gas is actually flat as oppsed to increasing usage of coal and oil.
Petroleum / Natural Gas will run out in the next 50 years. 97% of fossil fuel reserves are coal. 20% of the world's coal supply is located in the United States.
Energy yield depends on how much carbon is contained in the coal. Two types dominate US reserves. Anthracite is 95% carbon and is approximately 300 million years old. Lignite is 25% carbon is nearly 150 million years old. Deposits are around 300 feet below the surface and typically 2-8 feet thick. Coal production has increased since 1970.At current usage, the supply will last 1500 years. However at a 5% growth rate the supply will last only 86 years. We can expect even greater usage as other fossil fuels become scarce.
 Shale Oil
Shale oil deposits in the US are found in southwestern Wyoming, eastern Utah, and western Colorado. Oil shale contains kerogen which, when burned, can be converted into fuel products. The amount of shale oil deposits are significantly greater than the amount of US petroleum deposits by a factor of ten. However, economic mining requires a yield of 25 gallons of oil per ton of shale. Only 30% of the known deposits meet this criteria. Of that 30%, only 15% is recoverable under present conditions. The refinement of shale is very difficult and requires large amounts of water. The bottom line is that shale oil is not economically viable at this point.
 Importance of fossil fuel
Fossil fuels are of great importance because they can be burned (oxidized to carbon dioxide and water), producing significant amounts of energy. The use of coal as a fuel predates recorded history. Coal was used to run furnaces for the melting of metal ore. Semi-solid hydrocarbons from seeps were also burned in ancient times,but these materials were mostly used for waterproofing and embalming.
Commercial exploitation of petroleum, largely as a replacement for oils from animal sources (notably whale oil) for use in oil lamps began in the nineteenth century.
Natural gas, once flared-off as an un-needed byproduct of petroleum production, is now considered a very valuable resource.
Heavy crude oil, which is much more viscous than conventional crude oil, and tar sands, where bitumen is found mixed with sand and clay, are becoming more important as sources of fossil fuel.Oil shale and similar materials are sedimentary rocks containing kerogen, a complex mixture of high-molecular weight organic compounds, which yield synthetic crude oil when heated (pyrolyzed). These materials have yet to be exploited commercially.These fuels are employed in internal combustion engines, fossil fuel power stations and other uses.
Prior to the latter half of the eighteenth century, windmills or watermills provided the energy needed for industry such as milling flour, sawing wood or pumping water, and burning wood or peat provided domestic heat. The wide-scale use of fossil fuels, coal at first and petroleum later, to fire steam engines, enabled the Industrial Revolution. At the same time, gas lights using natural gas or coal gas were coming into wide use. The invention of the internal combustion engine and its use in automobiles and trucks greatly increased the demand for gasoline and diesel oil, both made from fossil fuels. Other forms of transportation, railways and aircraft also required fossil fuels. The other major use for fossil fuels is in generating electricity and the petrochemical industry. Tar, a leftover of petroleum extraction, is used in construction of roads.
 Environmental effects
In the United States, more than 90% of greenhouse gas emissions come from the combustion of fossil fuels.Combustion of fossil fuels also produces other air pollutants, such as nitrogen oxides, sulphur dioxide, volatile organic compounds and heavy metals.
According to Environment Canada:
"The electricity sector is unique among industrial sectors in its very large contribution to emissions associated with nearly all air issues. Electricity generation produces a large share of Canadian nitrogen oxides and sulphur dioxide emissions, which contribute to smog and acid rain and the formation of fine particulate matter. It is the largest uncontrolled industrial source of mercury emissions in Canada. Fossil fuel-fired electric power plants also emit carbon dioxide, which may contribute to climate change. In addition, the sector has significant impacts on water and habitat and species. In particular, hydro dams and transmission lines have significant effects on water and biodiversity."
According to U.S. Scientist Jerry Mahlman and USA Today: Mahlman, who crafted the IPCC language used to define levels of scientific certainty, says the new report will lay the blame at the feet of fossil fuels with "virtual certainty," meaning 99% sure. That's a significant jump from "likely," or 66% sure, in the group's last report in 2001, Mahlman says. His role in this year's effort involved spending two months reviewing the more than 1,600 pages of research that went into the new assessment.
Combustion of fossil fuels generates sulfuric, carbonic, and nitric acids, which fall to Earth as acid rain, impacting both natural areas and the built environment. Monuments and sculptures made from marble and limestone are particularly vulnerable, as the acids dissolve calcium carbonate.
Fossil fuels also contain radioactive materials, mainly uranium and thorium, which are released into the atmosphere. In 2000, about 12,000 tonnes of thorium and 5,000 tonnes of uranium were released worldwide from burning coal.It is estimated that during 1982, US coal burning released 155 times as much radioactivity into the atmosphere as the Three Mile Island incident.However, this radioactivity from coal burning is minuscule at each source and has not shown to have any adverse effect on human physiology.
Burning coal also generates large amounts of bottom ash and fly ash. These materials are used in a wide variety of applications, utilizing, for example, about 40% of the US production.
Harvesting, processing, and distributing fossil fuels can also create environmental concerns. Coal mining methods, particularly mountaintop removal and strip mining, have negative environmental impacts, and offshore oil drilling poses a hazard to aquatic organisms. Oil refineries also have negative environmental impacts, including air and water pollution. Transportation of coal requires the use of diesel-powered locomotives, while crude oil is typically transported by tanker ships, each of which requires the combustion of additional fossil fuels.
Environmental regulation uses a variety of approaches to limit these emissions, such as command-and-control (which mandates the amount of pollution or the technology used), economic incentives, or voluntary programs.
An example of such regulation in the USA is the "EPA is implementing policies to reduce airborne mercury emissions. Under regulations issued in 2005, coal-fired power plants will need to reduce their emissions by 70 percent by 2018".
In economic terms, pollution from fossil fuels is regarded as a negative externality. Taxation is considered one way to make societal costs explicit, in order to 'internalize' the cost of pollution. This aims to make fossil fuels more expensive, thereby reducing their use and the amount of pollution associated with them, along with raising the funds necessary to counteract these factors.
Former CIA Director James Woolsey recently outlined the national security arguments in favor of moving away from fossil fuels.
 Advantages and disadvantages
The discovery of fossils for energy purpose has turned the wheel of revolution in the history of mankind. Fossil fuels have the capacity to satisfy the energy demands of the entire world for several hundred years. Fossil fuels have provided a great impetus to the industrial revolution that took place in the twentieth century. the modern world greatly owes its technological and mechanical progress to fossil fuels. However, the irrational consumption of fossil fuels have lead to several problems all over the world.
Fossil fuels have several advantages over other sources of energy. This is the main reason why they are still the major energy supplier of the world. The advantages of fossil fuels are as follows:
- Fossil fuels have a very high calorific value. Thus, burning 1 gm of fossil fuel releases tremendous amount of energy.
- The reservoirs of fossil fuels are pretty easy to locate.
- Coal is a fossil fuel that is found in abundance. It is used in most power plants because it reduces the production cost to a great extent.
- Transportation of fossil fuels that are in liquid or gaseous forms is very easy. They are simply transported through pipes.
- Construction of power plants that work on fossil fuels is also easy.
- Petroleum is the most predominantly used form of fossil fuels for all types of vehicles.
- Fossil fuels are easier to extract and process, hence are cheaper than the non-conventional forms of energy.
Fossil Fuels were a preferred source of energy until recently, their over consumption and some undersirable properties have lead to several issues of grave importance. The disadvantages of fossil fuels are as follows:
- Although, oil, natural gas and coal are found in abundance in nature, the alarming rate at which they are being consumed has resulted in substantial depletion of their reservoirs.
- The hydrocarbons present in the fossil fuels, release greenhouse gases, such as Methane, Carbon dioxide etc. Which are capable of damaging the ozone layer.
- Besides, other harmful gases such as carbon monoxide and sulfur dioxide are responsible for Acid Rain, which has spelled disaster for ecology.
- Extraction of fossil fuels has endangered the environmental balance in some areas. Moreover, Coal mining has jeopardized the lives of several mine workers.
- The depletion of reservoirs has made the extraction of fossil fuels an expensive affair. This is likely to affect the fuel prices in near future.
- Leakage of some fossil fuels, such as natural gas, crude oil can lead to severe hazards. Hence, transportation of these fuels is very risky.
- Fossil fuels have contributed in more than one way for global warming, the issue that is been discussed all over the world.